Afterglow Studies Eric Torrence University of Oregon 183 nd LMTF Meeting 10 October 2013

Eric TorrenceSeptember Overview Test afterglow model by single-bunch addition  Originally studied by Mika  Will need to be used for 25 ns operations Try to test assumptions in method  Afterglow is universal with time and μ  Afterglow is additive to the prompt luminosity signal (not true if there are migration effects) Look at expected afterglow levels in 2015 (using 2012 templates) Look at ns fills

Eric TorrenceSeptember Fills Single-bunch templates  r bunches, μ~20, first fill of 2012  r bunch, μ~50, high-mu test Test runs  r bunches in mini-train  r ns physics fill - during BCM noise period  r ns physics fill - after BCM noise period  r ns fill - 97 bunches  r ns fill bunches Large range in mu, 3 months apart

Eric TorrenceSeptember Details Looked only at OR algorithms (simpler), mainly:  BcmH_EventOR  BcmV_EventOR  Lucid_HitOR No absolute calibrations applied, everything scaled to some relative luminosity Simple log formulas, no complicated Lucid mu dependence L = -ln(1-Rate)

Eric TorrenceSeptember BCMV single-bunch response r BcmVOR Single-bunch, high μ Peak = 1, used to normalize relative response Afterglow falls below noise level after ~500 BCIDs Colliding bunch Afterglow Noise

Eric TorrenceSeptember BCMV single-bunch response r BcmVOR Single-bunch, high μ Averaged over many LBs Afterglow Reflections More plots in appendix...

Eric TorrenceSeptember Stability over short time BCMV: Lucid:

Eric TorrenceSeptember Stability over long times r r BcmVOR ~ identical over x2 in mu and three months!

Eric TorrenceSeptember Lucid HitOR r No reflections Short-term falloff Similar mid-term slope Longer tail (or just lower noise?)

Eric TorrenceSeptember Single-beam Templates r BCM BCIDs to reach ~10 -7 level LucidHit BCIDs to reach ~10 -7 level (ran into next bunch) Constant background subtracted from -100 BCIDs

Eric TorrenceSeptember Maximum BCM afterglow Just add 500 copies of this template (without peak), each shifted by 1 BCID Asymptotic value 0.8% reached in ~200 BCIDs

Eric TorrenceSeptember Maximum Lucid Hit afterglow Even with longer tail, less ‘integral’ afterglow (no reflections) Asymptotic value 0.3% reached in ~300 BCIDs

Eric TorrenceSeptember ns limits BCID-1 works for BCM in 2012! (coincidental, only for BcmV) Afterglow under collisions ~ Difference w/ BCID-1 ~ 1 x (worse in 2011) 0.4% is half of 25 ns limit (expected) colliding bcid ± 1

Eric TorrenceSeptember Realistic 25 ns fill pattern 14 25ns_2604b_2592_2288_2396_288bpi12inj.sch 2604 bunches colliding in P1/5 Mostly saturated (except at start-of-train)

Eric TorrenceSeptember Data subtraction procedure (per LB) Start with raw luminosity by BCID for each lumi block Identify colliding bunches, and divide out average colliding luminosity from full distribution  not strictly necessary, but useful for averaging over LBs  also avoids need for calibration, everything relative... Build model of afterglow by adding up templates, one template per collision BCID, weighted by relative lumi Subtract this afterglow from raw luminosity in all BCIDs Iterate if desired (practically makes little effect) Measure residual background in abort gap (last 50 BCIDs) Subtract background as well to produce corrected lumi

Eric TorrenceSeptember Example 6 colliding bunches (normalized response) 500 BCID template length constant term ‘fit’ here Raw Luminosity After.+Bgd. Prediction

Eric TorrenceSeptember Example Zoomed 6 colliding bunches rather excellent agreement between predicted and observed afterglow under collisions

Eric TorrenceSeptember Lucid artifacts Finite Lucid template leads to (small) artifacts with few bunches 1500 BCIDs constant term ‘fit’ here

Eric TorrenceSeptember Lucid HitOR Prediction close to luminous bunches looks right on (high μ template, 28 tubes)

Eric TorrenceSeptember Lucid - 50 ns fill Works fine with full fill pattern Remember: simple log formula applied, no mu dependence

Eric TorrenceSeptember BcmV noise comparison During BCM noise period After BCM noise period << 10-3 discrepancies

Eric TorrenceSeptember ns runs Can’t prove afterglow under collisions is correct, but procedure seems to work fine

Eric TorrenceSeptember ns runs Can’t prove afterglow under collisions is correct, but procedure seems to work fine Same train length and gap expected in 2015

Eric TorrenceSeptember Lucid reduced HV Lucid ran with reduced HV for most runs from r215433, includes all 25 ns runs Template clearly not accurate

Eric TorrenceSeptember Lucid reduced HV 2 Scale up fast component (BCID+1, 2) by ~30% Seems to work fine!

Eric TorrenceSeptember ns Lucid Hit OR Use scaled template to look at 25 ns Lucid data Much larger afterglow (~2%) due to HV settings normalized background error slight mismatch

Eric TorrenceSeptember ns comparison Compare afterglow-subtracted relative luminosity collisions only Shape looks familiar, but magnitude is larger...

Eric TorrenceSeptember ns comparison 28 Similar to Benedetto’s plots? Remember, no complicated Lucid corrections, just log formula

Eric TorrenceSeptember Trigger Counters Special-purpose counters to look at 6 L1 items before and after veto to study deadtime by BCID Can try to use before veto as a proxy for luminosity Triggers available  Counter 0 is trigger 93 L1_MU11  Counter 1 is trigger 85 L1_EM30  Counter 2 is trigger 102 L1_J50  Counter 3 is trigger 128 L1_FJ75  Counter 4 is trigger 118 L1_XE50  Counter 5 is trigger 97 L1_J10 Must be skeptical, many trigger-related issues with bunch train position... Trigger rates ~1% error per BCID (over many LBs) Most linear with lumi

Eric TorrenceSeptember ns run L1_EM30 L1_MU11 L1_MU11 low at start of train (retriggering?) L1_EM30 rises in early train (calo noise?)

Eric TorrenceSeptember ns run L1_EM30 Now referenced to Lucid, L1_MU11 looks pretty OK...

Eric TorrenceSeptember ns run Back end of bunch train seems to be more consistent with BcmV

Eric TorrenceSeptember ns run Really had to draw any conclusions from this

Eric TorrenceSeptember Conclusions Single-bunch template method seems to work for 2012  Templates quite universal over all 2012 Afterglow error using BCID-1 appears smaller than 2011 for BcmVOR No evidence of anything weird in BCM noise period 25 ns data shows larger (as expected) but manageable afterglow levels, Lucid larger due to HV settings First look at Lucid/BCM ratios is rather alarming, but probably lots to understand here Trigger rates don’t seem to help

Eric TorrenceSeptember Appendix A Single-bunch plots Run bunches, μ ~ 20

Eric TorrenceSeptember Lucid Hit OR

Eric TorrenceSeptember Lucid OR

Eric TorrenceSeptember Lucid OR A

Eric TorrenceSeptember Lucid OR C

Eric TorrenceSeptember Lucid AND Raw rate only!

Eric TorrenceSeptember BcmH OR

Eric TorrenceSeptember BcmV OR

Eric TorrenceSeptember BcmH OR A From Rates: A + C = OR + AND

Eric TorrenceSeptember BcmV OR A From Rates: A + C = OR + AND

Eric TorrenceSeptember BcmH OR C

Eric TorrenceSeptember BcmV OR C

Eric TorrenceSeptember Appendix A Single-bunch plots Run bunch, μ ~ 40

Eric TorrenceSeptember Lucid Hit OR

Eric TorrenceSeptember Lucid AND Raw rate only!

Eric TorrenceSeptember BcmH OR

Eric TorrenceSeptember BcmV OR

Eric TorrenceSeptember BcmH OR A From Rates: A + C = OR + AND

Eric TorrenceSeptember BcmV OR A From Rates: A + C = OR + AND

Eric TorrenceSeptember BcmH OR C

Eric TorrenceSeptember BcmV OR C